SE538603C2 - Chuck arrangement - Google Patents

Description

20 25 30 538 603 The present invention solves the above described problems.

Hence, the invention relates to a backing chuck jaw part having a first central axis and a contact surface perpendicular to said first central axis, which backing chuck jaw part is ar- ranged to engage with a clamping chuck jaw part having a second central axis, in which engagement the contact surface is arranged in contact with a corresponding contact surface on said clamping chuckjaw part so as to together form a chuckjaw for a chuck, which back- ing chuckjaw part is characterized in that the backing chuckjaw part is manufactured from a harder metal material than a metal material from which the clamping chuck jaw part is manufactured, in that a cross-section of the backing chuck jaw part along said first central axis comprises a convex structure, and in that the convex structure is arranged to engage with a corresponding concave structure of a cross-section along said second central axis of the clamping chuckjaw part so that the said concave structure is permanently deformed as a res ult of an engagement between said convex and said concave structures resulting from the backing and clamping chuckjaw parts first being arranged in a contacting orientation, in which the first and second central axes, respectively, are aligned with each other and the respective contact surfaces are facing each other, and thereafter being pressed together into an engagement orientation, in which contact is established between said contact sur- faces.

The invention also relates to a clamping chuckjaw part having a second central axis and a contact surface perpendicular to said second central axis, which clamping chuckjaw part is arranged to engage with a backing chuck jaw part having a first central axis, in which en- gagement the contact surface is arranged in contact with a corresponding contact surface on said backing chuck jaw part so as to together form a chuck jaw for a chuck, which clamp- ing chuckjaw part is characterized in that the backing chuckjaw part is manufactured from a harder metal material than a metal material from which the clamping chuck jaw part is manufactured, in that a cross-section of the clamping chuck jaw part along said second central axis comprises a concave structure, and in that the concave structure is arranged to engage with a corresponding convex structure of a cross-section along said first central axis 10 15 20 25 30 538 603 of the backing chuckjaw part so that the said concave structure is arr anged to be perma- nently deformed as a result of an engagement between said convex and said concave struc- tures resulting from the backing and clamping chuckjaw parts first being arranged in a con- tacting orientation, in which the first and second central axes, respectively , are aligned with each other and the respective contact surfaces are facing each other, and thereafter being pressed together into an engagement orientation, in which contact is established between said contact surfaces.

Furthermore, the invention relates to a method for operating a chuck, which method is characterized in that the method comprises the steps a) providing said at least two backing chuckjaw parts on the chuck; b) providing said at least two clamping chuck jaw parts, the respective concave structure of which has not yet been permanently deformed as a conse- quence of engagement with a backing chuckjaw part; c) mounting said clamping chuck jaw parts on said backing chuckjaw parts, and bringing the respective chuck jaw parts into re- spective engagement with their respective contact surfaces in direct contact with each other so that the said respective concave structure is permanently deformed by the corre - sponding convex structure of the respective backing chuck jaw part; d) clamping a work- piece using the chuck; e) releasing the workpiece; f) demounting the clamping chuck jaw parts from the backing chuck jaw parts; g) again mounting the clamping chuck jaw parts on the same respective backing chuck jaw parts; and h) again clamping the same or another workpiece using the chuck. In the following, the invention will be described in detail, with reference to exemplifying embodiments of the invention and to the enclosed drawings, wherein: Figure 1 is a perspective view from the top of a chuckjaw according to the present invention; Figure 2 is a perspective view from the bottom of the chuck jaw of figure 1; Figure 3 is a perspective view similar to the one shown in figure 1, but with a cross-section removed; 10 15 20 25 30 538 603 Figure 4 shows the chuck jaw of figure 3, with the same cross-section removed, in a detail perspective view; Figure 5 is a perspective view from above of a clamping chuck jaw part according to the present invention with said cross-section removed; Figure 6 is a detail perspective view from below showing the clamping chuck jaw part of figure 5; Figure 7 is a perspective view from above of a backing chuck jaw part according to the present invention with said cross-section removed; Figure 8 is a view which is similar to the one shown in figure 7, but without any removed cross-section; Figure 9 is a top view of a chuck according to the present invention; and Figure 10 is a flowchart illustrating a method according to the invention.

All figures show the same chuck, chuckjaw and ch uckjaw parts, respectively, from different angles and with different component parts removed and / or with the same cross-section removed. Furthermore, all figures share the same set of reference numerals. In the following description, it is referred to all figures 1-9 as applicable.

A chuck 10 according to the present invention comprises a number of chuck jaws 100, which may or may not be identical and are used to clamp a workpiece 12 from one respective radial direction of the chuck 10 each. Each chuckjaw 100 may comprise a backing chuckjaw part 120 and a clamping chuckjaw part 110. The backing chuck jaw part 120 is fastened to a main body 11 of the chuck 10. The clamping chuckjaw part 110 is fastened to the respec- tive backing chuck jaw part 120 and contacts the workpiece 12 when clamping the latter.

According to the invention, the backing chuckjaw part 120 has a first central axis A1 and a contact surface 123 perpendicular to the first central axis A1. Furthermore, according to the invention the backing chuckjaw part 120 is arra nged to engage with a respective clamping chuck jaw part 110 according to the invention, which has a second central axis A2 and a respective contact surface 113 which is perpendicular to the second central axis A2. 10 15 20 25 30 538 603 ln the said engagement between the two respective chuck jaw parts 110, 120, the contact surface 123 is arranged in contact with the corresponding contact surface 113, so that the backing chuck jaw part 120 together with the clamping chuck jaw part 110 forms a chuck jaw 100 according to the invention for use as a part of a chuck 10 according to the invention (see in particular figure 9).

Further according to the invention, the backing chuck jaw part 120 is manufactured from a harder metal material than a metal material from which the clamping chuckjaw part 110 is manufactured.

Moreover, there is defined firstly a contacting orientation of the clamping chuck jaw part 110 with respect to the backing chuck jaw part 120, as well as an engagement orientation of the clamping chuckjaw part 110 with respect to the backing chuckjaw part 120. ln both these orientations, the said first A1 and second A2 axes are aligned and preferably overlap- ping, and the said contact surfaces 113, 123 face each other, and are preferably parallel one to the other.

Secondly, there is defined a cross-section C of the chuck jaw 100, and hence of both the backing 120 and the clamping 110 chuck jaw parts, when in said contacting orientation as well as when in said engagement orientation. The cross-section C runs along said first A1 and second A2 axes in said contacting and engagement orientations, in otherwords the axis A1, A2 both extend within the cross-section C plane. The cross-section C illustrated in the figures constitutes an example of such a cross-section.

Then, according to the invention, the cross-section C of the backing chuckjaw pa rt 120 com- prises a convex structure 126 and the cross-section C of the clamping chuck jaw part 110 comprises a corresponding concave structure 116. To be clear, the convex structure 126 is a two-dimensional geometric structure generated by a corresponding three-dimensional structure which is part of the backing chuckjaw pa rt and which, when seen in the said cross- section C, generates the convex structure 126. As such, the said three-dimensional structure 10 15 20 25 30 538 603 may very well be, and preferably is, a convex structure as well, at least locally convex. The corresponding is true regarding the structure 116 or the clamping chuck jaw part 110, but with concave two- and three-dimensional structures instead of convex ones. ln the above mentioned contacting orientation, the convex structure 126 and the concave structure 116 preferably come into direct contact with each other, thus stopping the chuck jaw parts 110, 120 from moving further towards each other along the axes A1, A2 without using a certain force strong enough to result in permanent deformation of the material forming the concave structure 116.

When a pressing force is applied to the chuck jaw parts 110, 120, pressing them towards one another from the said contacting orientation along the axes A1, A2, the concave struc- ture 116 is permanently deformed as a result of the engagement between the convex struc- ture 126 and the concave structure 116. ln other words, a permanent dent, track or the like is formed in the relatively softer material of the concave structure 116 by the convex struc- ture 126 pressing against a surface 116a of the concave structure 116. When the contact surfaces 113, 123 are fully pressed together so that contact is established between them, the engagement orientation has been achieved.

Since the deformation ofthe clamping chuckjaw part 110 is permanent, when the clamping chuck jaw part 110 is detached from the backing chuck jaw part 120, from the said engagement- ment orientation, and then re-attached at a later point in time, no or only very limited pres- sure will be required to again arrange the chuckjaw parts 110, 120 in the engagement ori- entation. Furthermore, it is preferred that the geometry of the convex structure 126 in com- bination with the geometry of the concave structure 116 is arranged so that the chuck jaw parts 110, 120, when again being brought together along the axes A1, A2 with the contact surfaces 113, 123 facing each other, again end up in the engagement orientation in a pre- dictable manner, for instance by using guides (providing full predictability in three direc- tions) or by having circular sym metric structures 116, 126 (see below ) (providing predictability in two directions but variability along a rotational direction). 10 15 20 25 538 603 As a result, a chuckjaw 100 according to the invention will predictably provide the same, or selectively partially the same, clamping geometry in relation to a workpiece 12 even after removal and reinstallation of the clamping chuck part device 110. lt is even possible to use the same backing chuck jaw part 120 with several different clamping chuck jaw parts 110 with the result that one and the same clamping chuck jaw part 110 predictably yields a desired clamping geometry every time it is used. Consequently, there is no longer any need for recalibration of clamping chuck jaw parts 110. ln particular, the fact that the two contact surfaces 113, 123 have contact in the said en- gagement orientation provides excellent axial precision ofthe chuckjaw 100.

According to a preferred embodiment, the backing chuckjaw part 120 is manufactured from annealed steel having a hardness of at least 500 HB, preferably between 550 and 600 HB.

Herein, “HB” relates to the standard Brinell hardness number. lt is at least the surface part, exposed to the engagement described herein, which is made from such material. The cor- responding is true regarding the clamping chuckjaw part 110.

The clamping chuckjaw part 110, on the other hand, is preferably either manufactured from a steel alloy having a hardness of at the most 250 HB, preferably between 100 and 250 HB, or from an aluminum alloy having a hardness of at the most 150 HB , preferably at the most 100 HB, preferably between 75 and 150 HB.

As mentioned above and as illustrated in the figures, it is preferred that both the convex structure 126 and the concave structure 116, respectively, are rotationally symmetric about the first A1 and second A2 central axis, respectively. lt is, however, possible that the convex 126 and / or concave 116 structure is or are only partly rotationally symmetric, such as com- prising convex or concave circular sections interrupted by straight corners, or the like, de- pending on the particular indexing needs. 10 15 20 25 30 538 603 Such complete or part-wise symmetry achieves that the said permanent material defor- mation also becomes rotationally symmetric about the second central axis A2, and as a re- sult the clamping chuck jaw part 110 can be rotated about the first axis A1 and in relation to the backing chuckjaw part 120 while still achieving full contact between the convex 126 and the concave 116 structures when in the engagement orientation at different rotational angles. This provides predictable and accurate clamping orientation for an indexable clamping chuckjaw part 110.

Namely, it is preferred that the chuck jaw 100 is indexed, so that said engagement between the chuck jaw parts 110, 120 is arranged so that the clamping chuck jaw part 110 can be turned in relation to the backing chuckjaw part 120 about the second central axis A2, so as to assume one of a number of predetermined rotational positions, and that the clamping chuck jaw part 110 is arranged with different clamping radii for different ones of said rota- tional positions. Such different clamping radii are illustrated in the figures, in which the clamping chuck jaw part 110 comprises sections 111 with larger radius and sections 112 with smaller radius.

According to a preferred embodiment illustrated in the figures, the convex structure 126 comprises an edge, preferably an edge which is at least partly circular symmetric about the fist axis A1, with a radius of curvature of between 1 and 5 mm, preferably of between 2 and 3 mm, preferably ofabout 2.5 mm.

According to a further preferred embodiment, the concave structure 116 comprises a sur- face 116a, preferably a conical surface, which is inclined in relation to the second central axis A2, preferably with an angle of inclination A, between an axis which is parallel to the second central axis A2 and the surface 116a, of between 15 ° and 40 °, so that the convex structure 126 strikes the said surface 116a when the chuck jaw parts 110, 120 are brought into said contact orientation. This embodiment is particularly useful in combination with the edge with certain curvature radius, as described above. 10 15 20 25 30 538 603 According to one preferred embodiment, the clamping chuckjaw part 110 is manufactured from a steel alloy, such as the one described above, in which case the angle of inclination A is between 18 ° and 26 °, preferably about 22 °. According to an alternative embodiment, the clamping chuck jaw part 110 is manufactured from an aluminum alloy, such as the one described above, in which case the angle of inclination is between 26 ° and 34 °, preferably about 30 °. Preferably, the surface 116a is straight or substantially straight as seen in the cross-section C.

As further illustrated in the figures, it is preferred that the backing chuck jaw part 120 com- prises an indentation 125, which is preferably rotationally symmetric about the first central axis A1, and the clamping chuck jaw part 110 comprises a corresponding protrusion 115, which is preferably rotationally symmetric about the second central axis A2. Then, it is pre- ferred that an envelope surface of the said indentation 125 is arranged to come into direct contact with a corresponding envelope surface of the said protrusion 115 when the chuck jaw parts 110, 120 are in the said engagement orientation, preferably in a way so that the relative position of the clamping chuck jaw part 110 in relation to the backing chuck jaw part 120, in a plane perpendicular to the second central axis A2, is locked when the chuck jaw parts 110, 120 are in said engagement orientation. This provides for excellent radial precision of the achieved clamping action.

According to a particularly preferred embodiment, when the said envelope surfaces are rotationally symmetric about the respective first A1 and second A2 central axis, the said enve- lope surfaces are arranged to come into direct contact along their entire respective angular extent when the chuck jaw parts 110, 120 are in the said engagement orientation. This is a simple yet robust way to achieve the said radial precision. ln particular, it is preferred that the said indentation 125 has a conical shape, narrowing from the contact surface 123 inwards, and that the protrusion 115 has a correspondingly conical shape, so that said full direct contact is established as the chuck jaw parts 110, 120 are pressed together into the said engagement orientation. 10 15 20 25 30 538 603 Preferably, the said convex structure 126 is constituted by an outer delimiting edge of said indentation 125. Correspondingly, it is preferred that the said concave structure 116 is con- stituted by an inner base corner of the said protrusion 115 .ln an alternative embodiment, the indentation 125 and the corresponding protrusion 115 are not conical, but cylindrical. This makes production simpler.

According to a preferred embodiment, the chuck jaw parts 110, 120 are geometrically ar- ranged so that a certain play, of between 0.05 and 0.25 mm, preferably between 0.10 and 0.15 mm, most preferably about 0.12 mm, is present between the said contact surfaces 113, 123 when the chuck jaw parts 110, 120 are arranged in said contact orientation. Con- sequently, it is this play which is then lessened and finally eliminated as the chuckjaw parts 110, 120 move from the contacting orientation to the engagement orientation by force.

Tests have shown that a play of this magnitude provides a sufficient permanent defor- mation in order to provide high precision in a predictable way, while still being able to easily move the chuck jaw parts 110, 120 into the engagement orientation during the first time of installation.

Furthermore, it is preferred that the chuck jaw 100 also comprises a screw means 130, ar- ranged to impa rt the force pressing the chuck jaw parts 110, 120 towards each other into the engagement orientation. The screw means 130 preferably runs in a centrally arranged through hole 114 of the clamping chuck jaw part 110, which through hole 114 is provided with a shoulder, and is fastened in a corresponding, threaded, central through hole 124 of the backing chuckjaw part 120 , thereby pulling the chuckjaw parts 110, 120 together. The chuck jaw 100 is then preferably arranged so that a screw means 130 moment of between 60-90 NI \ / I, preferably between 70-75 NM, is required for the said contact to be established.

Tests have proven that this provides an adequate permanent material deformation while at the same time providing a reasonable work ergonomics and minimized risk of undesired material damage. 10 10 15 20 25 30 538 603 Hence, a chuckjaw 100 according to the invention comprises a backing chuckjaw part 120 as described above, and a clamping chuck jaw part 110 also as described above. Further- more, a chuck 10 according to the present invention preferably comprises at least two, pref- erably at least three, such chuck jaws 100, and is further associated with a third central axis A3 (out from paper in figure 9). Preferably, the chuck 10 further comprises a respective radial setting means (illustrated schematically as 121) for each respective chuck jaw 100, arranged to act on the backing chuck jaw part 120 of the chuck jaw 100 in question and allow it to be set radially in relation to said third central axis A3 to a desired location in relation to the clamped workpiece 12. lt is noted that figures 1-4 illustrate the above described engagement orientation of the chuck jaw parts 110, 120, in which the contact surfaces 113, 123 are in full contact. lt is preferred that there is a play 101 in this case, of at least 1 mm, between an end of the above described protrusion 115 and a bottom of the above described indentation 125.

Figures 7 and 8 also show areas 127 of removed material, in order to decrease the weight of the backing chuckjaw part 120.

Figure 10 illustrates the method steps of a method according to the present invention. ln a first step, the at least two, preferably three, backing chuck jaw parts 120 of the chuck 10 are provided and mounted on the chuck 10. ln a second step, the at least two clamping chuck jaw parts 110 are provided. ln a third step, the said clamping chuckjaw parts 110 are mounted on the respective backing chuck jaw parts 120. ln this step, the respective concave structures 116 of the clamping chuckjaw parts 110 have not yet been permanently deformed as a consequence of engagement- ment with the corresponding backing chuck jaw part 120. ln other words, the respective chuck jaw part 110, 120 pairs are in their respective contacting orientation after this third 11 10 15 20 25 30 538 603 step, and the clamping chuck jaw part 110 has not been in the engagement orientation before. ln a fourth step, the at least two respective chuckjaw part pairs are brought into the above described engagement orientation in relation to the other. Hence, each respective chuck jaw part 110, 120 is brought into a respective engagement with their respective contact surfaces 113, 123 in direct contact with each other, so that the said respective concave structure 116 is permanently deformed according to what has been described above. ln a fifth step, a first workpiece 12 is clamped using the chuck 10, and is thereby fixed in a predetermined position for machining or the like. This step preferably also comprises a cal- ibration substep, in which the backing chuck jaw parts 120 are adjusted in a respective di- rection perpendicular to the third axis A3 so as to achieve said predetermined position. With a chuck 10 according to the present invention, such a calibration needs only be done once for each set of clamping chuckjaw parts 110. The next time a workpiece is to be clamped, the adjustment of the chuck jaws 100 along the direction perpendicular to the third axis A3 can be set directly, preferably automatically, without the need for separate calibration. ln a sixth and a seventh step, the position of the respective chuck jaw 100 when the first workpiece 12 is clamped by the chuck 10 is noted, as well as the positions of the backing chuck jaw parts 120, in the said respective direction perpendicular to the third axis A3. At least the latter noting can be accomplished automatically, by a CNC machine or the like, in which the chuck 10 is used, measuring and storing electronically the adjustment positions of the backing chuck jaw parts 120. ln an eighth step, the first workpiece 12 is released. ln a ninth step, the clamping chuckjaw parts 110 are demounted from the respective back- ing chuckjaw parts 120. 12 10 15 20 25 30 538 603 ln a tenth step, which may be performed at a later point, and in particular after use of the chuck 10 with its backing chuck jaw parts 120 for similar or other purposes and together with other sets of clamping chuckjaw parts, the originally used set of clamping chuck jaw parts 110 are again mounted on the same respective corresponding backing chuckjaw parts 120.

Finally, in an eleventh step, the same workpiece 12, or another workpiece, is again clamped by the chuck 10.

Preferably, in the clamping in the tenth step, the respective chuckjaw 110 is caused to re- turn to the position, in the respective direction perpendicularto the third axis A3, previously noted in the seventh step.

However, at least one clamping chuck jaw part 110 may be rotated about its respective second central axis A2 as compared to its respective position after the fourth step, depending on the geometry of the workpiece which is clamped in the eleventh step.

Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications may be made to the described embodiments without de- parting from the basic idea of the invention.

For instance, the shape of the chuckjaw parts 110, 120 may differ from the ones illustrated in the figures.

Also, the backing chuck jaw parts 120 may be more complex, or feature other types of ad- justment means, than illustrated in the figures and described above.

Hence, the invention is not to be considered limited to the described embodiments, but may be varied across the full scope of the enclosed claims. 13

Claims (19)

10 15 20 25 30 538 603 CLAIMS 1. Backing chuckjaw part (120) having a first central axis (A1) and a contact surface (123) perpendicular to said first central axis, which backing chuck jaw part is arranged to engage with a clamping chuckjaw part (110) having a second central axis (A2), in which engagement the contact surface is arranged in contact with a corresponding contact surface (113) on said clamping chuck jaw part so as to together form a chuck jaw (100) for a chuck (10), characterizedizedin that the backing chuck jaw part is manufactured from a harder metal material than a metal material from which the clamping chuck jaw part is manufactured, in that a cross-section (C) of the backing chuckjaw part along said first central axis comprises a convex structure (126), and in that the convex structure is arranged to engage with a corresponding concave structure (116) of a cross-section (C) along said sec- ond central axis of the clamping chuckjaw part so that the said concave structure is perma- nently deformed as a result of an engagement between said convex and said concave struc- tures resulting from the backing and clamping chuckjaw parts first being arranged in a con- tacting orientation, in which the first and second central axes, respectively, are aligned with each other and the respective contact surfaces are facing each other, and thereafter being pressed together into an engagement orientation, in which contact is established between said contact surfaces. 2. Backingchuckjawpart (120) accordingtoclaim1, c h a r a c t e r i s e d i n that the backing chuckjaw part is manufactured from annealed steel having a hardness of at least 250 HB, prefer lead between 250 and 300 HB. Clamping chuckjaw part (110) having a second central axis (A2) and a contact surface (113) perpendicular to said second central axis, which clamping chuck jaw part is arranged to engage with a backing chuck jaw part (120) having a first central axis (A1), in which en- gagement the contact surface is arranged in contact with a corresponding contact surface (123) on said backing chuck jaw part so as to together form a chuck jaw (100) for a chuck (10) , characterized in that the backing chuckjaw part is manufactured from a harder metal material than a metal material from which the clamping chuckjaw part 14 10 15 20 25 30 538 603 is manufactured, in that a cross-section (C) of the clamping chuckjaw part along said second central axis comprises a concave structure (116), and in that the concave structure is ar- ranged to engage with a corresponding convex structure (126) of a cross-section (C) along said first central axis of the backing chuck jaw part so that the said concave structure i s arranged to be permanently deformed as a result of an engagement between said convex and said concave structures resulting from the backing and clamping chuck jaw parts first being arranged in a contacting orientation, in which the first and second central axes, respectively, are aligned with each other and the respective contact surfaces are facing each other, and thereafter being pressed together into an engagement orientation, in which con- tact is established between said contact surfaces. Clamping chuck jaw part (110) according to claim 3, characterizedin that the clamping chuck jaw part is either manufactured from a steel alloy having a hardness of at the most 250 HB, preferably between 100 and 250 HB, or from an aluminum alloy having a hardness of at the most 250 HB, preferably at the most 100 HB, preferably between 50 and 100 HB. 5. Chuck jaw part (110,120) according to any one of the preceding claims, char - acterisedin that both the convex structure (126) and the concave structure (116) are at least partly rotationally symmetric about the first (A1) and second ( A2) central axis, respectively. 6. Chuck jaw part (110,120) according to any one of the preceding claims, char - acterisedin that the convex structure (126) comprises an edge witha radius (r) of curvature of between 1 and 5 mm, preferably of between 2 and 3 mm, preferably of about 2.5 mm. 7. Chuck jaw part (110,120) according to any one of the preceding claims, char - acterisedin that the concave structure (116) comprises a surface (116a) which is inclined in relation to the second central axis (A2), preferably with an angle (A) of 15 10 15 20 25 30 538 603 inclination of between 15 ° and 40 °, so that the convex structure (126) strikes the said sur- face when the chuck jaw parts are brought into said contact orientation. Chuck jaw part (110,120) according to claim 7, characterizedin that the clamping chuck jaw part is manufactured from a steel alloy, and in that the angle (A) of inclination is between 18 ° and 26 °, preferably about 22 °, alternatively that the clamp- ing chuck jaw part is manufactured from an aluminum alloy, and in that the angle (A) of inclination is between 26 ° and 34 °, preferably about 30 °. 9. Chuck jaw part (110,120) according to any one of the preceding claims, char - acterisedin that the backing chuckjaw part comprises an indentation (125) and the clamping chuck jaw part comprises a corresponding protrusion (115), and in that an envelope surface of the said indentation is arranged to come into direct contact with an envelope surface of the said protrusion when the chuck jaw parts are in the said engagement- ment orientation. 10. Chuck jaw part (110,120) according to claim 9, characterizedin that the said envelope surfaces are rotationally symmetric about the respective first (A1) and second (A2) central axis, and in that the said envelope surfaces are arranged to come into direct contact along their entire respective angular extent when the chuck jaw parts are in the said engagement orientation. 11. Chuck jaw part (110,120) according to claim 9 or 10, c h a r a c t e r i s e d i n that the said convex structure (126) is constituted by an outer delimiting edge of said indentation (125). 12. Chuckjaw part (110,120) according to any one of the preceding claims, charac - terisedin that the chuck jaw parts are arranged so that a certain play, of be- tween 0.05 and 0.25 mm, preferably between 0.10 and 0.15 mm, preferably about 0.12 mm , between the said contact surfaces (113,123) is present when the chuck jaw parts are arranged in said contact orientation. 16 10 15 20 25 30 538 603 13. Chuck jaw (100) comprising a backing chuck jaw part (120) according to any one of the preceding claims as dependent on claim 1 as well as a clamping chuck jaw part (110) according to any one of the preceding claims as dependent on claim 3. 14. Chuck jaw (100) according to claim 13, characterizedizedin that the chuckjaw further comprises a screw means (130) arranged to impart the said pressing force pressing the chuckjaw parts (110,120) towards each other in order to achieve said engagement- ment orientation , and in that the chuckjaw is arranged so that a screw means moment of between 60-90 NI \ / I, preferably between 70-75 NM, is required for the said contact to be established. 15. Chuckjaw (100) according to claim 13 or 14, characterizedizedin that the chuckjaw is indexed, so that said engagement between the chuck jaw parts (110,120) is arranged so that the clamping chuck jaw part can be turned in relation to the backing chuck jaw part about the second central axis (A2) so as to assume one of a number of pre-determined rotational positions, and in that the clamping chuck jaw part is arranged with different clamping radii (111,112) for different ones of said rotational positions. 16. Chuck (10) comprising at least two chuck jaws (100) according to any one of claims 13-15, characterized in that the chuck is associated with a third central axis (A3), and in that the chuck further comprises a respective radial setting means (121) for each respective jaw, arranged to act on the backing ch uckjaw part ofthe ch uckjaw in ques- tion and allow it to be set radially in relation to said third central axis. 17. Method for operating a chuck (10) according to claim 16, c h a r a c t e r - i s e d i n that the method comprises the steps a) providing said at least two backing chuckjaw parts (120) on the chuck; b) providing said at least two clamping chuckjaw parts (110), the respective con- cave structure (116) of which has not yet been permanently deformed as a consequence of engagement with a backing chuckjaw part; 17 10 15 20 h) 18. at least one clamping chuck jaw part (110) is rotated about its respective second central axis Method accordingto claim 17, characterized 538 603 mounting said clamping chuckjaw parts on said backing chuckjaw parts, and bringing the respective chuck jaw parts into respective engagement with their respective contact surfaces (113,123) in direct contact with each other so that the said respective concave structure is permanently deformed by the corre- sponding convex structure (126) of the respective backing chuckjaw part; clamping a workpiece (12) using the chuck; releasing the workpiece; demounting the clamping chuckjaw parts from the backing chuckjaw parts; again mounting the clamping chuck jaw parts on the same respective backing chuckjaw parts; and again clamping the same or another workpiece using the chuck. (A2) as compared to its respective position after step c. 19. comprises noting the position ofthe respective chuckjaw (100) when the workpiece (12) is clamped by the chuck (10), and step h comprises again causing the respective chuck jaw to Method accordingto claim 17 or 18, characterized return to the noted position. 18 i n that, in step h, at i n thatstepd